Electronic switching apparatus



April 2], 1942. A. (P. KING v 2,280,528

ELECTRONIC SWITCHING APPARATUS Filed April 26, 1940 G795 F/LL EDINVENTOR By A. 1-? KING A T TOR/V5 V Patented Apr. 21, 1942 1 ELECTRONIOSWITCHING APPARATUS Archie P. King, Red Bank, N. J., assignor to BellTelephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application April 26, 1940,Serial No. 331,715

Claims. (Cl. 250-27) This invention relates to electronic switchinapparatus, and more particularly to an arrangement for controlling thetime constant of individual electronic tubes embodied in such apparatus.

Heretofore, electronic switching apparatus has been employed forcollecting signals from geographically spaced antennas such thatthermionic amplifiers associated with each antenna are renderedoperative as electronic tubes individual to each antenna ionizeseriatim. Signals of at least a predetermined magnitude received overthe antenna connected to the operative amplifiers serve to arrestionization of the electronic tubes. This condition obtains so long asthe signals maintain the predetermined magnitude. Signals below suchmagnitude allow the electronic tubes to resume ionization whichcontinues until another antenna and the operative amplifiers associatedtherewith supply signals of requisite magnitude to arrest ionization.Such apparatus is disclosed in the patent of A. P. King et al. No.2,136,621, granted November 15, 1938.

The ionization period of the individual electronic tubes embodied inapparatus according to the above patent is controlled by a grid timeconstant RtCt. A residual charge on the capacity Ct may occasioninaccuracies in such time constant, particularly if there is a tendencyto reduce it to a relatively small value. Accordingly, this inventioncontemplates an electronic switching arrangement in which the timeconstant of the individual gaseous discharge tubes is independent of thecharge on the capacity Cc.

A general object of the invention is to control the time constant of theindividual gaseous discharge tubes embodied in electronic switchingapparatus.

Another object is to precondition the individual tubes before a flow ofspace current is efiected therein.

A further object is to institute ionization in a certain tube in advanceof others in such apparatus.

The invention will be more readily understood from the followingdescription taken together with the accompanying drawing, the singlefigure of which illustrates the invention in its preferred embodiment.

As hereinbefore mentioned, a plurality of gas- .eous discharge tubes hasbeen arranged such that a discrete voltage pulse is effected on theoccasion of the institution of ionization in each thereof. This iscaused toltake place seriatim.

Each ionization period depends upon the time constant RtCt of theindividual tubes. Thus, ionization of one tube serves to charge acapacity Ct associated with. a succeeding tube until such chargenullifies the grid biasing voltage normally applied to the latter tubewhereupon ionization is instituted therein.

In a preferred embodiment, the invention comprises a resistance having anegative tempera- .ture coefiicient of resistance, such as boron,

pitchblende, etc., disposed in the anode circuit of each tube to controlthe time constant thereof. As each tube is ionized, the temperature ofsuch resistance increases due to a flow of space l current in theanode-cathode circuit thereof.

A life of the individual gaseous discharge tubes embodies a network ofelectromagnetic relays to delay the application of the anode voltage tothe tubes until the cathodes thereof have attained a certaintemperature. Also, a further feature includes the starting of theswitching apparatus such that ionization is instituted only in one tubeat a given time. As the latter involves the, presence of a grid biasingvoltage, the

application of the anode voltage serves to energize an electromagneticrelay which applies ground momentarily to the grid of a certain tube. Asa consequence, this tube ionizes in advance of others.

Referring to the drawing, a multiple tube switching circuit [0,comprising gas-filled electron discharge tubes ll, I2 and I3, isarranged so that the individual tubes ionize seriatim in acounter-clockwise direction in a manner that will be subsequentlyexplained. The number of suchdevices is equal to the number of switchingoperations to be performed. For example, the switching circuit Ill maybe utilized in a signal collecting systemto render operative a pair ofamplifiers and an antenna associated therewith, not shown, in the mannerpointed out in the patent of A. P. King et al., supra. Accordingly, thediscrete voltage pulses effected to accomplish such operation areavailable at terminals I4, I 5 and [6 relative to ground while a signalvoltage to maintain any one of the tubes in the ionized condition issupplied across the terminals II, II. A more detailed description ofthis arrangement may be had by referring to the patent of A. P. King etal., supra.

The cathode heaters of the tubes II, I2 and I3 are energized bysecondary winding 2| of a transformer 31 whose primary winding isconnected to commercial power input terminals 20, 2B which are appliedacross a suitable alternating current source, not shown. Steady gridbiasing current flows in a circuit comprising grounded battery 22,across the terminals II, II connected to lead 21, resistances 23 and 26associated with the tube I3, lead 28 and ground ZQ. As the resistances24 and 9 associated with the tube I2 bridge the leads 21 and 28 inseries, thesteady biasing current from the biasing source 22 also fiowstherethrough. Likewise, as the resistances 25 and 3|! associated withthe tube II shunt the leads 21 and 28 in series, the steady biasingcurrent from the biasing source 22 flows therethrough.

Consequently, the voltages developed across the resistances 23, 24 and25 serve to supply the necessary bias to the grids of the respectivetubes II, I3 and I2 to maintain the latter normally in a deionizedcondition. The negative biasing voltages developed across theresistances 3|], 9 and 26 prevent ionization of the respective tubes II,I2 and I3 except in a manner that will be presently explained. Theanodes of tubes II and I2 are directly joined by a capacity I8; those oftubes I2 and I3 by a capacity I9; and those of tubes I3 and II by acapacity 3|. In series with the anodes of the respective tubes II, I2and I3 are resistances 35, 8 and 65. A circuit organization of thisgeneral character has been utilized in an antenna switching system inthe manner pointed out in the patent of A. P. King et al., supra.

In accordance with this invention, resistances 36, and 66, connected inseries with the anodes of the respective tubes II, I2 and I3, compriseboron, pitchblende, or other material having a negative temperaturecoefiicient of resistance. The thermal inertia of these resistancesserves to control the time constants of the individual gaseous dischargetubes in a manner that will be hereinafter explained.

A power supply 34 includes the transformer 31 whose primary winding 38is connected across the commercial power terminals 20, 20 and whosesecondary winding 39 energizes the cathodes of a pair of rectifier tubes40,. 48. The anodes of the latter are energized by means of a pair ofsecondary windings 4|, 4|. Inductances 42 and 43, together withcapacities 44, 44, constitute a low-pass filter for reducing ripplevoltages. Secondary winding 33 is connected both to the filter and anelectromagnetic relay 45 with which is associated an electromagneticrelay 45 and a source 48 of direct current. Relay 45 is preferably aslow-acting or thermal type. Disposed in the output of the filter is anelectromagnetic relay 41 whose contacts are associated with the relays45 and 46 and the secondary windings 4|, 4| in a manner that will bepresently described. A lead 49 connects the positive terminal of thefilter to a terminal 58 which is common to the anodes of the tubes II,I2 and I3.

An automatic starting circuit 52 serves to institute ionization in thetubes I I, I2 and I 3, when starting, such that but one thereof isionized at a time, thereby conditioning the switching circuit III forthe operations that will be subsequently explained. This startingcircuit comprises a resistance 53 having one terminal connected to thelead 49 and its opposite terminal connected through the winding of anelectromagnetic relay 54 and a capacity 55 and resistance 56 in parallelto ground 51. A normally open contact 53 associated with the relay 54and grounded at 59 may be applied through a capacity 50 and resistance6| in parallel and a lead 62 to the grid of tube II as will besubsequently mentioned.

In operation, a switch 53, connected in series With one of the inputterminals 20, is closed to apply an alternating current voltagesimultanecusly to the cathode heaters of tubes II, I2 and I3 fromsecondary winding 2 I. At the same time, a voltage is also impressed bymeans of transformer 37 on the input of the power supply 34. After apredetermined interval, say, for example, of the order of one minute,the thermal relay 45 operates due to its operating circuit comprisingthe secondary winding 33, operating winding of relay 45, lead 56,normally closed front contact 61 of relay 41, lead 68 and lead 69returning to the secondary winding 33.

This causes contact III associated with relay 45 to apply the directcurrent source'48 to the operating winding of the relay 46. The latteroperates to complete the alternating current input circuit for therectifiers 40, 40 as the midpoint of the secondary windings 4|, 4|applied to the anodes thereof is now connected by lead 'II, closedcontact I2 of relay 46 and lead 69, returning to the input of thefilter. Now, the direct current voltage available across the output ofthe filter is applied to relay 41 which operates to lock in thealternating current input circuit for the rectifiers 40, 4|) by means ofa circuit comprising the mid-point of the secondary windings 4|, 4|,lead I3, closed back contact I4 of relay 4?, lead 68 and lead 69returning to the input of the filter. As the front contact 61 of relay41 is now opened, relay 45 is deenergized to open the operating circuitof relay 46 which also becomes deenergized. This interrupts thealternating current input circuit completed via lead 'II and closedcontact I2 of relay 46 as hereinbefore mentioned.

Anode voltage for the tubes II, I2 and I3 is supplied thereto on thelead 49. In connection therewith the time delay provided by the thermalrelay 45 serves to withhold the application of this voltage until thecathode heaters of the gas discharge tubes II, I2 and I3 and of therectifier tubes 40, 40 attain normal operating temperatures. This tendsto extend the useful life of the respective tubes.

At the instant the direct current voltage be comes available at theoutput of the filter embodied in the power supply 34, a surge of currentpasses through the resistance 53 and operating winding of the relay 54to charge the capacity 55. Relay 54 operates to close its contact 53.This applies ground to the grid of tube I I through a circuit comprisingground 59, closed contact 53, capacity 53 and lead 52. Consequently, thenormal biasing voltage developed across the resistance 23 and impressedon the grid of tube II, as previously explained, is now grounded. Inother words, a surge of current passing through the resistance 23charges the capacity 60, thereby depriving the grid of tube II of itsnormal biasingvoltage. This will cause the tube II to ionize in advanceof the tubes I2 and I3, both of whose attaches grids are supplied withnormal biasing voltage.

The resistance 56 connected in parallel with the capacity 55 serves todischarge the condenser 55 during intervals of non-use of the startingcircuit 52. For the constants, resistance 53=50,000 ohms, capacity55=0.1 micromicrofarad and the winding of relay I=1500 ohms, the surgeof current through the latter closed the contact 58 for a period of theorder of A second. In this illustration the resistance 56 is 500,000ohms, thereby giving the capacity 55 in parallel therewith a timeconstant of substantially 0.05 second. Capacity 60 is approximately 75micromicrofarad and the resistance 6| in parallel therewith may have anysuitable value to discharge the capacity 60 during periods of :non-useof the starting circuit 52.

The switching circuit III is so arranged that the tubes ionize in thecounter-clockwise order of II, I2, I3, II, I2 Asthetube II is nowionized in the manner above described, space current flows in itsanode-cathode circuit which includes ground I5 embodied in the filter ofthe power supply 34, lead 49, common terminal 50, resistance 35,resistance 35 having negative temperature coefficient of resistance,anode-cathode circuit of tube II, resistance 30 and ground 29. Prior tothe ionization of tube II, there was no flow of space current in theresistance 36 which in such condition manifests its maximium resistance.However, when the tube I I was ionized, the flow of space current in theresistance 36 began to increase the temperature of the latter andthereby to reduce the efiective resistance thereof.

As the temperature of the resistance 36 increases, the amount of thefiow of space current in the anode-cathode circuit of tube II increasescorrespondingly. This means that there is a gradually increasingpositive voltage being developed across the resistance 30 embodied inthe anode-cathode circuit of tube II as hereinbefore mentioned. Thispositive voltage increases until it has attained an amount which issufficient to render ineffective the negative biasing voltage producedacross the resistance 25 and applied to the grid of the tube I2. Thistends to render the grid of the tube I2 less negative until the value ofthe grid-trip voltage thereof is attained, whereupon the ionization oftube I2 is instituted to produce a flow of space current in itsanodecathode circuit.

Once ionization is instituted in the tube II, it may be terminated onlyby removing the posi tive voltage from the anode thereof, which voltagein this illustrationis substantially 150 volts. This is accomplished bymeans of the anode resistances 35 and 8 and the capacity I8, all ofwhich are utilized as follows: The initial anode voltage of 150 voltsapplied to anodes of the tubes II and I2 was decreased, for example, by110 volts, when ionization was instituted in each thereof, that is, to40 volts. When tubes II and I2 were in the deionized condition, eachside of the capacity I8 had a potential of 150 volts acting through theresistances 35 and 8. As tube II was the first to ionize, the potentialon both sides of the capacity I8 was decreased, for the purpose ofillustration, to 40 volts for an instant.

Accordingly, the voltages applied to the anodes f the tubes II and I2were also lowered to 40 volts for the same instant. As tube II continuesto ionize, the side of capacity I8 connected thereto will remain at apotential of 40 volts while the side connected to the deionized tube I2will be returned to a potential of 150 volts. When ionization wasinstituted in tube I2, the potential applied to both sides of thecapacity I8 wasagain lowered by volts, for an instant. Hence, thepotential applied to the anodes of the tubes II and I2 was also loweredby 110 volts, for the same instant.

As the potential on the side of capacity I8 connected to tube II was 40volts, it is now decreased, for an instant, by 110 volts, that is, bythe algebraic sum of 40 and 110, or to an instantaneous value of 70volts. For the same instant, the potential impressed on the anode oftube I I was also '70 volts. The side of condenser I8 connected to tubeI2 was also lowered by 110 volts and now remains at a steady 40 volts.The change of the anode voltage of tube II from 40 volts to aninstantaneous 70 volts serves to extinguish the ionization of tube I I,thereby terminating the flow of space current therein. Consequently, theinitial volts is again applied to the anode of tube II and to the sideof capacity I8 connected thereto. At the same time, a potential of 40volts is applied to the anode of tube I2 and to the side of capacity I8connected thereto. For a more detailed explanation of the extinguishmentof ionization in tube II, reference is made to the patent of A. P. Kinget al., supra.

Similarly, as the tube I2 ionizes, space current flows in itsanode-cathode circuit comprising ground I5 embodied in the filter of thepower supply circuit 34, lead 49, common terminal 5f), resistance 8,resistance 5I having a negative temperature coeflicient of resistance,anode-cathode circuit of tube I2, resistance 9, lead 28 and ground 29.As the temperature of the resistance 5| increases and, therefore, as itseffective resistance value decreases, the amount of the flow of spacecurrent in the anode-cathode circuit of tube I2 increasescorrespondingly. Consequently, there is an increasing positive voltagedeveloped across the resistance 0. This positive voltage increases untilit has attained an amount which is sufficient to render ineffective thenegative biasing voltage produced across the resistance 24 and appliedto the grid of tube I3, as hereinbefore explained. This tends to renderthe grid of tube I3 less negative until the value of the grid-tripvoltage thereof is attained whereupon ionization of tube I3 isinstituted to produce a flow of space current in its anodecathodecircuit. At the instant tube I3 was ionized, the side of the capacity I9connected to tube I2 has its potential lowered to an instantaneous ()70volts, which voltage was applied to the anode of tube I2 for the sameinstant to extinguish ionization therein, and the side of the capacityI9 connected to tube I3 was lowered to (+)40 volts.

Likewise, as the tube I3 ionizes, space current flows in theanode-cathode circuit comprising ground I5 embodied in the filter of thepower supply 34, lead 49, common terminal 50, resistance 65, resistance66 having a negative temperature coefiicient of resistance,anode-cathode circuit of tube I3, resistance 26, lead 28 and ground 29.As the temperature of resistance 66 increases and, therefore, as itseffective resistance value decreases, the amount of the flow of spacecurrent in the anode-cathode circuit of tube I3 increasescorrespondingly. Accordingly, there is an increasing positive voltageproduced across the resistance 26. This positive voltage increases untilit has attained an amount which is adequate to counteract'the negativebiasing voltage produced across the resistance 23 and applied to thegrid of tube II. This tends to render the grid of tube ll less negativeuntil the value of the grid-trip voltage thereof is reached, whereuponthe ionization of tube H is instituted to effect a, flow of spacecurrent in the anodecathode circuit thereof. At the instant tube II wasionized, the side of capacity 3| joined to tube !3 had its potentialreduced to an instantaneous ()70 volts, which voltage was applied to theanode of tube l3 for the same instant to extinguish ionization therein,and the side of the capacity 3| connected to tube H was lowered to (+)40volts.

As the tubes ll, l2 and i3 ionize in the order mentione dhereinbefore,the voltages developed across the respective resistances 30, 9 and 26and available at the terminals l5, I6 and it serve to provide pulseswhich may render operative a pair of amplifiers and the antennaassociated therewith in a signaling collecting system or perform otherfunctions as pointed out in my patent, supra. Thus, the period ofionization of the individual tubes ll, l2 and I3 is controlled by therespective resistances 36, and 66 whose individual value, when cold, maybe of the order of 20,000 to 100,000 ohms and, when heated, may bereduced to 1000 ohms or less. The time required to effect suchresistance change is a function of the thermal inertia of a particularresistance unit, which inertia is dependent upon the mass, heatcapacity, heat radiation and loss of heat by conduction. Theseresistances are capable of efiecting time constants of the order of afraction of a second, and may be mounted in the envelope of theindividual gas tubes when vacuum mounting is required.

What is claimed is: r

1. An electronic switching apparatus comprising in combination aplurality of gaseous discharge tubes each of which, embodies a grid, acathode and an anode, circuit means embodying said tubes and arranged toinstitute ionization in each thereof seriatim to produce discretevoltage pulses, said circuit means comprising means including aresistance element individual to each tube to apply biasing voltage tothe grid of a next succeeding tube to render all said tubes normallyinoperative, and means to control the time constant of ionization ofeach tube including a pair of resistance elements connected in series inthe anode-cathode circuit of each of said tubes, one of said pair ofresistance elements providing a voltage to counteract the biasingvoltage applied to said next succeeding tube and i the other of saidpair of resistance elements possessing a negative temperaturecoefiicient of resistance; means to apply voltage to the anodes of saidtubes, and electromagnetic means responsive to the initial operation ofsaid anode voltage means to apply ground potential momentarily to thegrid of a certain tube to effect ionization therein in advance of theother tubes so that the flow of space current in the anodecathodecircuit of said ionized certain tube in creases as the effectiveresistance of said resistance element connected in the anode-cathodecircuit of said ionized certain tube and possessing the negativetemperature coeflicient of resistance decreases in response tothe'increase in the temperature thereof due to the increase in the flowof space current to cause a corresponding increase in the counteractingvoltage produced across said one resistance element of s id pair of r stance emen individ al to said ionized certain tube to render ineffectivethe grid biasing voltage applied to the grid of said next succeedingtube to institute ionization therein, each pair of resistance elementsconnected in the anode-cathode circuit of each tube and each gridbiasing resistance element individual to each tube functioning in likemanner to institute ionization in each next succeeding tube.

2. An electronic switching apparatus comprising in combination aplurality of gaseous discharge tubes each of which embodies a grid, acathode and an anode, circuit means embodying said tubes and arranged toinstitute and extinguish ionization in each thereof seriatim to producediscrete voltage pulses, said circuit means comprising a plurality ofcapacities, circuit connections to connect the terminals of each of saidcapacities to the anodes of adjacent pairs of tubes, a source of gridbiasing voltage, circuit connections to apply said grid biasing sourceto the grids of said tubes, a resistance element individual to each ofsaid tubes and disposed in said grid biasing connections to applybiasing voltage to thenext succeeding tube to normally render all saidtubes inoperative, circuit connections to connect the cathodes of saidtubes including a resistance element individual to the anode-cathodecircuit of each tube to provide a voltage to counteract the grid biasingvoltage applied to the next succeeding tube, and circuit connectionsincluding a common terminal and a, resistance element in seriestherewith and individual to the anodecathode circuit of each of saidtubes, each of said last-mentioned resistance elements possessing anegative temperature coefiicient of resistance; means to energize thecathodes of said tubes, means to supply voltage to said common terminaland thereby to the anodes of said tubes so that the same voltage isapplied to both terminals of each of said anode capacities, and meansresponsive to said anode voltage to reduce the grid biasing voltage on acertain tube, when starting, to a value which is less by at least apredetermined amount than the grid biasing voltage applied to the othertubes so as to institute ionization in said certain tube in advance ofthe other tubes, said last-mentioned means comprising electromagneticmeans operated in response to a surge of the anode voltage to applymomentarily ground potential to the grid of said certain tube, the flowof space current in theanode-cathode circuit of said certain tubeincreasing as the effective resistance of said resistance elementconnected therein with said common terminal decreases with increases inthe temperature thereof to .cause corresponding increases in the voltageproduced across said counteracting voltage resistance element individualto the anodecathode circuit of 'said certain tube until the biasingvoltage impressed on the next succeeding tube is rendered suflicientlyless negative to institute ionization therein, the ionization of saidnext succeeding tube serving to change from a positive to a negativevalue the voltage applied to the terminal of said capacity connected tothe anode of said certain tube to extinguish ionization therein, saidresistance elements and said capacity associated with each adjacent pairof said tubes functioning in like manner to institute ionization in thenext succeeding tube and to extinguish ionization in the next precedingtube, each cycle of instituting ionization in one tube and extinguishingthe same in the other t me ei llga di re volta e pu e.

1 3, In combination, a gaseous discharge tube having a grid, means toapply a biasing voltage to the grid to maintain said tube normally in anonionized state, means to counteract the biasing voltage to instituteionization in said tube, means to extinguish ionization in said tube,and means having a negative temperature coefiicient of resistance andresponsive to a flow of space current due to ionization in said tube toactuate said counteracting means to determine the time interval ofionization of said tube.

In combination, a plurality of gaseous discharge tubes each having agrid, means-to apply a biasing voltage to the grids to maintain saidtubes normally in a non-ionized state, and means to render said biasingmeans ineffective with regard to individual tubes such that ionizationis instituted in said tubes in sequence to produce a series of discretevoltage pulses, said rendering means including a resistance elementhaving a negative temperature coefificient of resistance and individualto each tube to be responsive to a fiow of space current occasioned byionization therein to actuate said rendering means to control the timeconstant of each of said voltage pulses.

5. In combination, a plurality of gaseous discharge tubes each having a,grid and anode, means to apply a negative biasing voltage to the gridsto maintain said tubes normally in a nonionized state, means to apply avoltage to the anodes of said tubes, electromagnetic means responsive toan initial operation of said anode voltage means to apply groundpotential momentarily to the grid of a, certain tube to eiTectionization therein in advance of the other tubes, and means operatedautomatically to render the biasing voltage applied to the grid of eachtube less negative by an amount which is sufiicient to instituteionization in said tubes in sequence to produce a series of discretevoltage pulses, said automatic means including a plurality of resistanceelements connected in said anode voltage means such that each resistanceelement is individual to one tube, each of said resistance elementspossessing a negative temperature coefiicient of resistance andresponsive to a flow of space current in a respective ionized tube tocontrol said automatic means such that each tube is ionized for apredetermined interval of time.

6. In combination, a plurality of gaseous discharge tubes each embodyinga grid, a cathode and an anode, and circuit means embodying said tubesand arranged to institute and extinguish ionization in each tubeseriatim to produce a series of discrete voltage pulses, said circuitmeans comprising means connecting the grids and cathodes of said tubesand including a resistance element individual to each tube to produce avoltage to bias the grid of the next succeeding tube to maintain saidtubes in a non-ionized state, and means connecting the anode-cathodecircuits of said tubes and including a resistance element individual toeach anode-cathode circuit to produce a voltage to counteract thebiasing voltage applied to the grid of the next succeeding tube toinstitute ionization therein, and a resistance element possessing anegative temperature coefficient of resistance and individual to eachanode-cathode circuit to control the time constant of ionization of eachtube, said lastmentioned resistance element, in response to a flow ofspace current in the anode-cathode circuit of a certain ionized tube,decreasing its effe tive sistan so that an increase in the space currentcauses -a corresponding increase in the voltage produced by saidcounteracting voltage resistance element individual to the anode-cathodecircuit of said certain ionized tube until the biasing voltage on thegrid of said next succeeding tube is sufficiently counteracted to allowionization therein,

7. In combination, a plurality of gaseous discharge tubes each embodyinga grid, a cathode, and an anode, means connecting the grids and cathodesto apply biasing voltage to the grids to maintain said tubes normally ina non-ionized state, means to apply a voltage having one polarity to theanodes of said tubes, means connecting the cathodes of said tubes andresponsive to a flow of space current due to ionization in a certaintube to control said grid biasing means such that the grid biasingvoltage applied to the next succeeding tube is rendered suflicientlyless negative to eiTect ionization in said latter tube, means embodiedin said anode voltage means and responsive to the simultaneousionization in both said certain tube and said next succeeding tube tocontrol said anode voltage means to apply to the anode of said certaintube a substantially instantaneous voltage having a, polarity oppositeto the polarity of the voltage initially applied thereto to extinguishionization in said certain tube, the institution of ionization in eachtube producing a, voltage pulse; and means having a negative temperaturecoefiicient of resistance and embodied in said anode voltage means to beresponsive to a flow of space current due to ionization in said certaintube to actuate said biasing voltage controlling means to fix the timeinterval of each of said voltage pulses.

8. An electronic system for producing voltage pulses comprising aplurality of gaseous discharge tubes each embodying a grid, a cathodeand an anode, means including a plurality of resistance elementsconnecting the grid and cathode of each tube to the grid and cathode ofthe next succeeding tube such that a voltage developed across aresistance element individual to each tube serves to bias the grid ofthe next succeeding tube to maintain said tubes in a nonionized state,means to apply a voltage having one sign to the anodes of said tubes,means including a plurality of resistance elements connecting theanode-cathode circuits of said tubes such that a voltage developedacross resistance element individual to the anode-cathode circuit of acertain tube in an ionized state serves to counteract the biasingvoltage applied to the grid of said next succeeding tube to instituteionization in said latter tube, means embodied in said anode voltagemeans and responsive to simultaneous ionization in both said certaintube and said next succeeding tube to apply a voltage having anothersign to the anode of said certain tube to extinguish ionization therein,each cycle of instituting ionization in one tube and extinguishingionization in another tube being accomplished in sequence to produce aseries of discrete voltage pulses, and means comprising a resistanceelement having a negative temperature coefficient of resistance andindividual to the anode-cathode circuit of each tube to be responsive toa flow of space current due to ionization in said certain tube tocontrol the voltage developed across said counteracting voltageresistance element individual to the anode-v catnode c rc of s id. ce aib n by to control the-time constant of each pulse of the series ofdiscrete voltage pulses.

9. An electronic apparatus for producing voltage pulses comprising aplurality of gaseous discharge tubes each embodying a grid and an anode,means to apply biasing voltage to the grids to maintain said tubesnormallyin a non-ionized state, means to apply a voltage having onepolarity to the anodes of said tubes, means including an electromagneticrelay and responsive to an initial operation of said anode voltage meansto apply ground potential momentarily to the grid of a certain tube toinstitute ionization therein in advance of the other tubes, meansresponsive to ionization in said certain tube to counteract the biasingvoltage on the grid of a next succeeding tube to institute ionization insaid latter tube, means embodied in said anode voltage means andresponsive to simultaneous ionization in both said certain tube and saidnext succeeding tube to apply to the anode of said certain tube avoltage having a polarity opposite to that of the voltage initiallyapplied theretoto extinguish ionization in said certain tube, each cycleof instituting ionization in one tube and extinguishing ionization inanother tube being accomplished seriatim to effect a series of discretevoltage pulses, and means having a negative temperature coefiicient ofresistance and individual to the anode of each tube to be responsive toa flow of space current due to ionization in said certain tube tocontrol said counteracting means to determine the time constant ofionizationof each tube.

and circuit means embodying said tubes and arranged to institute andextinguish ionization in each thereof seriatim to effect a series ofdiscrete voltage pulses, said circuit means comprising means to applybiasing voltage to said grids to maintain said tubes normally in anon-ionized state, means to apply voltage having one polarity to theanodes of said tubes, means responsive to ionization in a certain tubeto produce a voltage which counteracts the biasing voltage applied tothe grid of a next succeeding tube to effect ionization in said lattertube, and means embodied in said anode voltage means and responsive tosimultaneous ionization in both said certain tube and said nextsucceeding tube to apply a, voltage of another polarity to the anode ofsaid certain tube to extinguish ionization therein, and means comprisinga resistance element having a negative temperature coefficient ofresistance and individual to each tube to be responsive to a, flow ofspace current in each tube to decrease its effective resistance as itstemperature increases to cause a corresponding increase in thecounteracting voltage produced by said counteracting voltage means untilthe biasing voltage applied to the grid of the next succeeding tube issufliciently counteracted to allow ionization therein,'the rate ofdevelopment of the counteracting voltage determining the time constantof ionization of each tube.

ARCHIE P. KING.

